I am building my 2nd sub (turning into quite a monster, but should be nice when done - pictures to come later) and was wondering if I am going to gain much with the second sub. It seems like the "Best" locations for a two sub setup could be one up front and one in the back of the theater, or one along the middle of each side wall. That won't work for me. I need to keep things up front behind my false wall.

So I am wondering if I will get much benefit from this or if I am just doing this to sound cool that I built my own sub, blah blah blah...

I saw this on another vendor's website, but wanted to run it past some "experts" here. The diagram isn't mine either, but shows the sub placement idea to match the words.

Try positioning the subs along the front wall with the woofer cone centers at the 1/4 and 3/4 distances of the room width. Rooms that are sympathetic with subs at these locations will yield almost as much bass output as corner placement but with a smoother overall frequency response. Of course, this reduces overall output compared to full corner placement, but most quality subwoofers nowadays have more than enough headroom to compensate.

Some of the older literature on sub placement is aimed at maximizing output (which would probably mean putting the subs together in a corner), but my impression from reading discussions on AVSforum is that there is a consensus these days for getting as smooth a bass in-room response as possible, for greatest fidelity, and that would probably mean keeping them apart, not both in a corner, and perhaps at different heights. The advice I have seen is to measure the response and do some experimenting with placement.

I have three subs in varying positions, one in the middle of a wall, one out near the middle of the room, and one in a closet. I haven't measured -- too much trouble. I listen to some jazz with a walking bass line, and if the notes don't fade in and out as they go up and down the scale, I figure I'm on the right track.

Right, old school of thought is to slap them in corners and get reinforced sound waves (perceived as louder), but I am hoping to smooth out the bass more than anything. Not that I have any (known) major problems. The room is about 14 feet wide, so using the 1/4 "rule" means 3.5 feet from the wall to the center of the woofer. I will have to do some measuring tonight when I get home to see how that fits with the bass traps and so forth behind the false wall.

I am pretty sure that my current single sub (SVS 20-39PCi) is at least 5 feet from the one side wall, maybe not.

I have one of my construction photos showing the sub between the left front speaker and the center (my memory had it out side of the left front speaker, but...):

It would seem that the subs should sit about where the M60s are currently at, bumping them inwards a little. Keep in mind that this picture is from BEFORE I built the stands to raise the M60s up a little and to get the VP180 up a lot off of the ground (in line with "ear height").

Nick, as you say, for the best effect in minimizing room modes, placement at the midpoints of opposite walls(or in diagonally opposite corners)is best. If the subs must both be placed along the front wall, the 1/4 placing shown is correct. As discussed by Dr. Toole and others, that placement serves to minimize or cancel some modes related to the width of the room. It has no effect on the modes related to room length, and doesn't have all the benefits of the placements described above, but is worthwhile.

I do need to update the room photos now that I have the crown molding with color changing LEDs and the LED/fiber optic star ceiling. For now, I am going to go to my build thread and add some subwoofer build pictures.